Metric Thread Pitch Reference Guide
| Diameter (mm) | Coarse (Standard) | Fine | Extra Fine | Super- fine |
|---|---|---|---|---|
| M1 | 0.25 | 0.2 | ||
| M1.6 | 0.35 | 0.2 | ||
| M2 | 0.4 | 0.25 | ||
| M2.5 | 0.45 | 0.35 | ||
| M3 | 0.5 | 0.35 | ||
| M3.5 | 0.6 | 0.35 | ||
| M4 | 0.7 | 0.5 | ||
| M5 | 0.8 | 0.5 | ||
| M6 | 1 | 0.75 | ||
| M7 | 1 | 0.75 | ||
| M8 | 1.25 | 1 | 0.75 | |
| M10 | 1.5 | 1.25 | 1 | 0.75 |
| M12 | 1.75 | 1.5 | 1.25 | 1 |
| M14 | 2 | 1.5 | 1.25 | 1 |
| M15 | 1 |
| Diameter (mm) | Coarse (Standard) | Fine | Extra Fine | Super- fine |
|---|---|---|---|---|
| M16 | 2 | 1.5 | 1 | |
| M17 | 1 | |||
| M18 | 2.5 | 2 | 1.5 | 1 |
| M20 | 2.5 | 2 | 1.5 | 1 |
| M22 | 2.5 | 2 | 1.5 | 1 |
| M24 | 3 | 2 | 1.5 | 1 |
| M25 | 1.5 | |||
| M27 | 3 | 2 | 1.5 | 1 |
| M30 | 3.5 | 2 | 1.5 | 1 |
| M35 | 1.5 | |||
| M36 | 4 | 3 | 2 | 1.5 |
| M42 | 4.5 | 3 | 2 | 1.5 |
| M48 | 5 | 3 | 2 | 1.5 |
| M56 | 5.5 | 4 | 2 | 1.5 |
| M64 | 6 | 4 | 3 | 2 |
Standard Descriptions
- ISO 4032: Standard height, Style 1 hexagon nuts (similar to DIN 934). Used for coarse threads.
- ISO 4035: Chamfered hexagon thin nuts. Used for lower-load applications or as lock nuts with coarse threads.
- ISO 8673: Standard height, Style 1 hexagon nuts with metric fine pitch thread.
- ISO 8674: Hexagon high nuts (Style 2) with metric fine pitch thread, offering greater thread engagement.
- ISO 8675: Hexagon thin nuts with metric fine pitch thread, suitable for locking purposes.
- ISO 8676: Hexagon head screws with metric fine pitch thread. Ideal for applications requiring fine adjustment.
- DIN 981: "KM" type locknuts with four slots, used for securing bearings on a shaft.
- DIN 70852: Slotted locknuts, often used with tab washers to prevent loosening.
This guide details metric thread pitch sizes for different bolt diameters. It covers four main thread types: Coarse (Standard), Fine, Extra Fine, and Superfine.
ISO 261 Standard Metric Thread Series
Metric threads are dimensioned by the nominal diameter followed by the pitch in millimetres - an M12 x 1.75 thread has a 12 mm major diameter and a 1.75 mm pitch. ISO 261 defines the standard diameter-pitch combinations for general-purpose metric threads, and every diameter has one preferred coarse pitch plus one or more fine alternatives shown in bold or normal text in this table. The pitch controls both the mechanical behaviour of the joint and the tooling required to cut or roll the thread.
Coarse, Fine, and Extra Fine Pitch
Coarse pitch is the default choice: it produces the strongest thread for the diameter, is fastest to machine, and is what most standard fasteners are supplied with. Fine pitch has a smaller helix angle, which gives better self-locking, more adjustment resolution, and greater tensile stress area on small diameters - at the price of a higher risk of thread stripping and damage. Extra fine and superfine pitches (0.75 mm and finer) appear on lock nuts and precision adjustment parts such as bearing locknuts, where fine increments and reliable locking outweigh the handling drawbacks.
When to Specify a Fine Pitch Instead
Choose a fine pitch when the joint must resist vibration loosening and you cannot add a secondary locking element, when you need very small axial adjustment steps (for example on feed screws or instrument components), or when the available thread engagement length is short. For hardened steel, thin wall sections, and high-strength fasteners, the fine pitch series also improves the stress distribution. When in doubt, keep the coarse pitch - it is the one stocked and tooled everywhere.
Frequently Asked Questions
What does the Metric Thread Pitch Reference Guide show?
It shows complete metric thread pitch specifications for all bolt diameters, including standard, fine, extra fine, and superfine pitches.
How do I use it?
Find your bolt diameter in the table to see the available thread pitch options — coarse, fine, or extra fine — for that size.
Is it free?
Yes. This Kod5 reference page is free to use in the browser.